The default settings on the Iphone are nice, but they never really seem to do what I want them to do, which is make it easier for me to keep everything in one place. To do that and still be happy about what it is I'm 'sharing' with the WORLD, I have to tweak the settings to everything. The calendar is one of those tweaks. The goal of this post is not to tell you about all the tweaks you can make to your calendar... that's completely up to you. But...if for some reason you find that you'd like to change the calendar that is sync'd with your IPhone... it's actually very easy. Follow the steps below and you'll have it done in about 30 seconds. On the iPhone, go to the Settings app. Go to the Mail, Contacts, Calendars settings. Scroll pretty far down the list to the Calendars section. One of the items there is the Default Calendar. Tap that and pick a calendar.